In order to rout a groove, slot, or recess into the side or edge of a workpiece, it is generally necessary to secure the workpiece by means of a clamp or the like, and to provide a stable supporting platform and a guiding fence for the router baseplate.
Some prior art clamps provide a support area on the top surface of the clamp jaws for supporting a router base or sub-base. One example of such a prior art clamp is found in De Cristoforo, R. J., The Portable Router Book, 2nd Edition (Blue Ridge Summit, Pa.: Tab Books, 1994) at pp. 131-134. FIG. 9-21 on p. 133 shows workpieces gripped between the jaws of a vise clamp. The workpieces are held lower than the top surfaces of the jaws which provide a support area for a router base or sub-base. The vise clamp, in turn, is secured to a bench vise. FIG. 9-22 on p. 133 shows the bottom-side of a router sub-base having two parallel adjustable guides attached to either side of an access hole for a router bit. The router sub-base is used in conjunction with the clamping arrangement shown in FIG. 9-21, as illustrated in FIG. 9-23 on p. 134.
While this prior art clamping and router sub-base apparatus is useful for making certain controlled router cuts into a workpiece, it suffers from a number of drawbacks. One drawback is that a router sub-base must be attached to the router for operation. While using a sub-base is desirable in certain situations (as demonstrated in some of the present inventor's co-pending applications), in the present application, making a precise router cut into a small, clamped workpiece can be made more difficult by the additional bulk of the sub-base and the friction of the parallel adjustable guides sliding along the outside of the clamps. In addition, it is assumed that the outer sides of the vise clamp are true and parallel to each other, which may not be the case.
Another drawback is that the device shown in the De Cristoforo reference is not designed to rout grooves that are wider than the router bit cutting diameter, although this could potentially be done if the guides are set wider than the width of the jaw clamps. However, since lateral or side-to-side movement is necessary in order to cut a groove or slot in the workpiece that is wider than the cutting diameter of the router bit (i.e. a rectangular groove or slot), the narrow support area formed by the top surface of the jaws of the vise clamp may cause the sub-base to become unstable if moved too far to the front or to the back. This is particularly a serious problem where the clamped workpiece is narrow and the jaws of the vise clamp are also narrow in comparison to the diameter of the router base.
Also, the construction details for the vise clamp, shown in FIG. 9-19, on page 132 of De Cristoforo, makes clear that the length of the workpiece is limited to what would fit between the two carriage bolts.
Finally, in the prior art apparatus, there is no apparent way to control the length of the router cut, nor is there a way to form a side-to-side straight edge at either end of a router cut. This precludes cutting a true rectangular groove or slot.